netdev - Re: [PATCH net-next] tcp: Change txhash on some non-RTO retransmits

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:   Wed, 12 Oct 2016 17:22:24 +0200
From:   Eric Dumazet <eric.dumazet@...il.com>
To:     Yuchung Cheng <ycheng@...gle.com>
Cc:     Lawrence Brakmo <brakmo@...com>, netdev <netdev@...r.kernel.org>,
        Kernel Team <Kernel-team@...com>,
        Neal Cardwell <ncardwell@...gle.com>
Subject: Re: [PATCH net-next] tcp: Change txhash on some non-RTO retransmits

On Tue, 2016-10-11 at 20:56 -0700, Yuchung Cheng wrote:

> I thought more about this patch on my way home and have more
> questions: why do we exclude RTO retransmission specifically? also
> when we rehash, we'll introduce reordering either in recovery or after
> recovery, as some TCP CC like bbr would continue sending regardlessly,
> so starting in tcp_ack() with tp->txhash_want does not really prevent
> causing more reordering.

Note that changing txhash during a non rto retransmit is going to break
pacing on a bonding setup, since the change in txhash will likely select
a different slave, where MQ+FQ are the qdisc in place.